I always find it odd when I encounter people who have a close friend or someone they like so they call that person by a family name, such as brother, even though they are not related… Or they make friends with someone who is older, so they call them dad.
The words brother, sister, dad, mom: these are not status levels of how close someone is to you. These are titles to define how someone fits in a blood relation with others. You can have a brother that you don’t like at all, but that does not change the fact that they are your bother. You could have someone that you love, and it does not make them your sister. Don’t believe me? Go look the definitions up (http://www.merriam-webster.com/).
As Random As Random Gets 